Is it actually waterproof? Simba - Odyssey September 27, 2017 10:59 Follow We've done our research and can confirm they are 100% waterproof - creating the perfect barrier from spills and stains. Related articles Is the Protector hypoallergenic? Can you take away my old mattress? Why should I choose a Simba Mattress Protector? What is the Protector made of? What sizes do you offer and will this fit other mattresses too?